I just bought a Sendero 300 RUM, I also picked up some 200 gr Accubonds and Barnes LRX's. I was hoping someone may have tried these and has some load data.
I can't help you with the 300RUM, but I can offer you this one bit of advice.
Make darn sure you thoroughly clean your bore before you switch bullets and repeat the process before switching back. The jacket material between the two is completely different & can foul VERY badly if you mix them together (ask me how I know ). Other than that, Tikkamike has some data floating around here for the LRX & Retumbo, do a search.
I like the AB's with 92g of H-1000. Its a max load. I have shot Elk from 50 to 621 yards and it has performed excellent. Shot a couple of deer, it might be a bit much for whitetail.
I havent had alot of luck with H1000 with 200 gr Noslers. I use a max charge of Retumbo in remington brass, and federal primers with great success. If I go back to 180gr, I may try H1000 again. YMMV though with each gun.